1. Field of the Invention
The present invention relates to a modified polysilazane. More particularly, the present invention relates to a modified polysilazane stabilized by reacting an inorganic polysilazane with an alcohol, an organic acid, an ester, a ketone, an aldehyde, an isocyanate, an amide, a mercaptan, an alkylamine, an alkylsilazane or an alkylaminosilane, and a process for the preparation thereof.
2. Description of the Related Art
Silicon nitride and silicon nitride-containing ceramics formed through a polysilazane as a precursor have an excellent high-temperature strength, thermal shock resistance and oxidation resistance, and therefore, are widely used as construction materials and functional materials in various industrial fields.
In general, a polysilazane is valuable as a precursor polymer for silicon nitride ceramics. The polysilazane is soluble in solvents, has an excellent moldability, and gives a high yield of ceramics, and further, is characterized in that the purity of ceramics after firing is high.
Processes for the preparation of inorganic polysilazanes and organic polysilazanes are known. Typically, a polysilazane can be prepared by reacting a halosilane with a Lewis base and reacting the obtained complex compound with ammonia (see, for example, Japanese Examined Patent Publication No. 63-16325).
A polysilazane, especially an inorganic polysilazane, has a low chemical stability, and an increase of the molecular weight and gelation readily occur, and accordingly, the handling property is poor. The stability of the polysilazane and the molecular structure thereof can be controlled to some extent by changing the kind of the halosilane used as the starting material of the polysilazane or changing the mixing ratio of at least two halosilanes, but this control is limited and difficult. Accordingly, the polysilazane is defective in that the handling thereof is poor, and the properties of ceramics by high-temperature firing are not uniform.